This invention relates to a flow restrictor for use in a flowmeter measuring the flow rate of fluid and, more particularly to an improved structure of a flow restrictor for use in a laminar flowmeter utilizing the pressure drop caused by laminar flow.
The laminar flowmeter is used to measure a flow rate according to the pressure drop, utilizing the phenomenon that when laminar fluid flows at a predetermined distance through a cylinder or between two planes, the pressure drop caused at the distance is substantially proportional to the volumetric flow rate of fluid which flows at the distance.
The flowmeter utilizing the above principle and the flow restrictor used therein are designed to comprise many thin passageways in order to obtain a sufficient quantity of laminar flow, for example, as explained in detail in U.S. Pat. No. 3,851,526 to Drexel. When it is desired to create a maximum possible pressure drop, each passageway should be formed as thin and elongate as possible. In conventional flowmeters, bundled thin pipes have been employed. In the above U.S. Pat. No. 3,851,526, further, there are disclosed a plurality of juxtaposed disks having a variety of complicated channels.
However, for the bundled pipes, it is difficult not only to manufacture each pipe but to secure the bundled pipes, resulting in increased costs. On the other hand, for the structure of a plurality of juxtaposed disks, each disk is complicated in manufacture and it is a troublesome procedure to arrange accurately the disks while positioning. These methods cost too much and are not suitable for mass production.